Considered the most striking representative of quartz, amethyst has always been coveted.
Queen Catherine the Great had a true adoration for this gem.
For a long time, it was considered as precious as sapphire, diamond and emerald.
.Today, due to the discovery of abundant deposits, it is no longer as valuable.
Its value has decreased – but its seductive beauty remains intact.
The violet or purple variety of quartz, the amethyst, besides being widely used as a gemstone until the 18th century, also has an aura of mysticism around it.
Many “powers” are attributed to it in different types of cultures. Some people say that the name amethyst comes from an ancient belief that this stone protected its owner from drunkenness.
The name amethyst comes from the Greek word “amethuskein”, where the “a” means not and the “methuskein” means intoxicate.
However, there are some controversies of the origin of the name.
Its colour comes from the presence of iron impurities and traces of aluminium, some varieties show the colours by exposure to radiation.
Colours range from purple or light purple to dark, with the dark ones with greater transparency being better regarded and consequently more expensive.
Some can change colour completely if subjected to heat treatment, as you will see later.
Amethyst does not have a homogeneous colour distribution. It appears in fragments, in uneven and/or external corners.
This characteristic often determines the type of cutting to better utilise the gem and its value.
Amethysts with perfect colour distribution are very rare and, when found, are very expensive.
1. Gemological characteristics
- Mineral class: quartz
- Crystal system: trigonal; six-sided prisms
- Chemical formula: SiO2
- Hardness: 7 mohs
- Density: 2.63 – 2.65
- Transparency: from transparent to translucent
- Colour: violet, purple, light to dark purple
- Brightness: vitreous
- Fluorescence: weak or absent
- Fracture: conchoidal, brittle
Amethyst is composed of an irregular overlapping of alternating sheets of quartz on the left and right sides.
As a result of this formation, amethyst can break with a wavy fracture or show “fingerprints”.
Some mineralogists apply the name amethyst to all quartz that exhibits this structure, regardless of its colour. The crystals always grow on a base.
When they are shaped like pyramids, the most intense colour predominates at the tips of these crystals.
There are some varieties of amethyst that may have white bands of milky quartz.
Amethysts are mainly found in the crystallised crusts of huge volcanic rocks such as basalt.
Amethysts are abundantly available at very affordable prices, but the most beautiful and valuable varieties are found in only a few places.
These have deeper purple or violet colours.
The most important deposits are in Brazil, but only around 3% of Brazilian amethysts are suitable for cutting and use in jewellery.
The others are used to make jewellery.
The others are used to make citrine and are also used in decoration or collections. Other important deposits are in Uruguay, India, Russia, Sri Lanka, Madagascar and the United States.
Argentina, Bolivia, Mexico, Namibia, Zambia, South Africa and Canada are also producers of amethyst.
Because they have different shades and nuances, they are often named after the country of origin, e.g. Brazilian amethyst, Bolivian, etc.
We have already talked about the 4C’s of diamond valuation.
Although it is a grading standard instituted by the GIA (Gemological Institute of America) for diamonds, it is the most accepted in the world and widely used for other gems and also by several laboratories, gemologists and expert appraisers.
Color, Carat, Clarity and Cut in Portuguese, colour, weight, purity and cut are the 4C’s that are used to evaluate amethysts as well.
The most valuable amethysts have a strong reddish purple and no colour zoning, i.e. the colour is evenly distributed throughout the stone. Very dark amethysts are not as valuable because there is a great reduction in lustre.
The presence of brown or bronze tones in amethysts also reduces their value. To identify some colour zoning by eye, buyers often place the amethyst on a table with a white surface.
- Degree of purity
Inclusions are one of the factors that determine the degree of purity of the amethyst. The fewer the inclusions, the higher the value and the better the grade.
Most faceted amethysts on the market do not have inclusions that are noticeable to the naked eye, but they are present in the vast majority of them. Fractures are also commonly found.
- Weight and Size
The weight of this gem is valued in carats. As with most gems, amethysts are found in various sizes and calibrated in millimetres.
Large centre stones are extremely commonly used and sold in the jewellery store, as long as the final price is not high.
- Cutting and Lapidation
As we have already said, most amethysts are faceted, to make better use of the colour distribution and also to locate as few inclusions as possible.
If these inclusions are very visible, they are cut into small cabochons or beads.
Oval, pear, emerald cuts, triangular, marquise and cushion are all widely used cuts.
Some arrangements and cut combinations appear in this gemstone such as step cuts and mixed faceted cuts. There are also diversifications of cuts called fancy cuts that display certain concave facets – these are usually mass-produced for certain collections.
Even animal sculptures are made with amethysts. In practice, the colour and purity of amethysts are the most important factors in their valuation. Due to the high supply, demand decreases, making it a relatively cheap and easy-to-buy gemstone.
However, amethysts do not fall out of fashion and are always present, both in expensive jewellery and in cheaper pieces.
4. Varieties of shades
Amethysts come in a wide variety of colours depending on their place of origin.
Those from Uruguay and Arizona have a deep purple-blue colour.
Amethysts from Russia are known as “Siberian” and have very deep colours with reddish and bluish tones.
They originate from deposits that have already been depleted and therefore have a higher price.
Africa produces amethysts with deeper colours than Brazil and other South American countries.
The term African amethyst can be used to refer to amethysts with different shades or darker colours, but it does not always mean that this is their origin.
Brazil, is considered the largest producer of amethysts, although most Brazilian amethysts are treated and sold as heated citrine. Here stones are available in all sizes and shapes.
The colours are not as good as those in Africa, but they meet the market demand.
5. Treatments and synthetics
Heat treatment can be used to lighten the colour of the amethyst when it is too dark, darken when light or remove brownish inclusions.
Ultraviolet radiation is also used to enhance or change the colour of amethysts.
Fracture treatments are rarely done, due to the high availability of specimens that do not show them to the naked eye.
Heat treatment causes an expansion of inclusions, which can generate fractures in the gem, it also increases the effect of colour zoning.
Usually, inclusions and zoning expansions are used to differentiate a treated amethyst from an untreated or synthetic one.
When amethyst is heated to high temperatures, around 470°C to 750°C, the iron impurities are reduced resulting in heated citrine.
Although this treatment is highly used, the colour obtained from citrine is not always permanent.
Most commercial citrine is actually amethyst or smoky quartz artificially heated.
However, the heat-treated stone may show differences, including a pinker colour characteristic of the original stone. The commercial value, however, is the same, at least in Brazil. Citrine quartz is a low-priced gemstone, cheaper than amethyst, but nevertheless highly prized and widely used in jewellery. Brazil and Scotland are the world’s largest producers of citrine. Brazil leads the production of amethyst, rose quartz and colourless quartz, with much of the production coming from Rio Grande do Sul.This variety of quartz is often used as a substitute for many yellow gemstones,such as topaz or sapphires.
Synthetic amethysts can be produced from hydrothermal methods, in which case small fragments of quartz and a solution of calcium carbonate, for example, are placed in a sealed container with high pressure.
This causes the crystals to fuse and recrystallise upon heating.
Some gem experts say that synthetic amethysts are widely mixed on the market with natural ones, but as identification tests – in their case – are not widely used, it cannot be said.
Others say the supply is so high that production of synthetic ones is limited to use in radios, watches and other electrical appliances.
In the old days, amethyst was widely used to protect individuals from drunkenness and intoxication, hence the name.
Today, people use amethysts to keep faith, bring peace and calm the spirit. It is said to strengthen wisdom and religiosity.
It prevents one from evil thoughts and actions, gives sensitivity in business and good health.
Oriental women wear it on their foreheads and believe that it gives positive energy to the Ajna chakra, also known as the “third eye”.
Amethyst is a very durable stone, but care should be taken to remove the jewellery in activities where the stone may suffer scratches.
It is important not to expose it to intense sunlight for a long time, radiation or black light. It can be easily cleaned with warm water and neutral soap, with a soft cloth or toothbrush. When storing, care should be taken not to place it with other harder stones, as scratches are inevitable.
Do not use chemical or abrasive products. The ideal is to wrap it in a soft cloth or a box lined with fabric.